This invention relates to an anchor insert adapted to be embedded in a concrete slab for cooperation with a pick-up unit which includes a locking stem having a pair of lift shoulders extending from opposite sides of the stem, to a concrete-excluding cage employed in such an insert, and to lifting apparatus constituting a combination of the anchor insert and such a pick-up unit.
The insert of the invention is designed for use primarily in connection with the relocation of a preformed concrete wall slab by a hoisting and tilting operation such as to lift the slab from an original horizontal position in which it was formed to a final vertical position which it will assume in constituting one wall of a concrete building installation. More particularly, the invention is concerned with an anchor insert and pick-up unit of the general type disclosed in U.S. Pat. No. 3,431,012. The present anchor insert is an improvement upon and provides advantages over the prior inserts.
An anchor insert is constructed of a plurality of rod or heavy wire sections which become embedded in a concrete slab and serve as anchor members for lifting the slab. A pick-up unit is provided for each anchor insert, and the unit is designed for releasably interengaging the insert. For the pick-up unit to engage the insert, it is necessary to shield portions of the insert from the surrounding concrete, and this has been accomplished by enclosing such portions in a concrete-excluding hollow cage, which may be constructed of plastic, metal or other suitable material. Hoisting apparatus is connected to the pick-up unit when the unit is engaged with the insert, and hoisting apparatus likewise may be connected to other similar pick-up unit and insert combinations disposed about the slab. The slab then may be raised from the horizontal position in which it is poured, to an upright position in which it may serve as a building wall, for example. The pick-up units are removed from their engagement with the inserts and may be used repeatedly with inserts in other slabs.
While the prior lifting apparatus of the type disclosed in the aforementioned patent is in widespread use, there remains room for improvement. In particular, the structure and assembly of the cage or can surrounding the thrust portions of the anchor rod sections in the insert of the patent render manufacture relatively laborious and time-consuming. It is necessary also to provide a good seal at each junction of the cage and an anchor rod, in order to prevent leakage of mortar into the cage, and the seal may not be reliable.